Two- and three-body photodissociation of gas phase I3

The photodissociation dynamics of I3− from 390 to 290 nm (3.18 to 4.28 eV) have been investigated using fast beam photofragment translational spectroscopy in which the products are detected and analyzed with coincidence imaging. At photon energies ⩽3.87 eV, two-body dissociation that generates I−+I2(A 3Π1u) and vibrationally excited I2−(X 2Σu+)+I(2P3/2) is observed, while at energies ⩾3.87 eV, I*(2P1/2)+I2−(X 2Σu+) is the primary two-body dissociation channel. In addition, three-body dissociation yielding I−+2I(2P3/2) photofragments is seen throughout the energy range probed; this is the dominant channel at all but the lowest photon energy. Analysis of the three-body dissociation events indicates that this channel results primarily from a synchronous concerted decay mechanism.